Heteroarylcarboxylic amides and esters are suitable intermediates for the preparation of a broad variety of compounds which are useful as agrochemicals or pharmaceuticals. In particular, they are key intermediates in the preparation of herbicidal aryloxyheteroarylcarboxamides which are described, for example, in EP 0 447 004 A or WO 94/27974.
European patent application EP 0 646 566 A suggests the hydrolyzation of trichloromethyl heteroarenes with water in the presence of chlorinated hydrocarbons and a Lewis acid, followed by reaction of the resulting heteroarylcarbonyl chloride with an amine. However, this process causes problems with respect to the rate and the exact equimolar addition of water. Any excess of water will cause hydrolysis of the desired acid chloride compound and therefore reduce the yields. Moreover, the use of chlorinated hydrocarbons is undesirable due to environmental problems, and a large amount of solvent is required. Furthermore, a very long (24 hour) reaction time using water/1,2-dichloroethane is necessary.
It is also known that pyridinecarboxylic acids are preparable by the hydrolysis of the corresponding (trichloromethyl)pyridine compound in a strong acid such as sulfuric acid or nitric acid (U.S. Pat. No. 3,317,549). German patent application DE 28 40 924 discloses a process in which benzotrihalides are treated with concentrated or fumic sulfuric acid. This process yields mixtures of benzoylhalides and halosulfonylbenzoylhalides.